As wireless local area network (WLAN) standards evolve, a WLAN system obtains a higher transmission rate by using higher bandwidth. In the standards, 20 MHz is usually used as a basic bandwidth unit. A bandwidth of 20 MHz is used in the 802.11a. The bandwidth is increased to 40 MHz in the 802.11n, and is increased to 80 MHz and 160 MHz in the 802.11ac. When the bandwidth is greater than 20 MHz, one 20 MHz channel is a primary 20 MHz channel, and a remaining 20 MHz channel is a secondary channel. In the current standards, when a station accesses a channel, a primary 20 MHz channel needs to be included. That is, when the primary 20 MHz channel is occupied, even if another channel is idle, the channel cannot be used. A channel bandwidth defined in the current standards has four modes: 20 MHz, 40 MHz, 80 MHz, and 160 (80+80) MHz.
In the next-generation WLAN standard 802.11ax, an intensive deployment scenario is mainly studied, and a study emphasis is turned from a peak throughput increment to spectral efficiency improvement. For a scenario in which stations supporting different WLAN standards intensively coexist, for example, for a scenario in which a station supporting 802.11n and a station supporting 802.11ax are intensively deployed, as shown in FIG. 1, each channel in FIG. 1 has a bandwidth of 20 MHz, an 802.11n station performs transmission by using a bandwidth of 20 MHz, and a spectrum is cut during narrowband transmission performed by the 802.11n station, causing channels available to an 802.11ax station to be discontinuous.
However, existing WLAN standards are short of an indication of a discontinuous channel in a frequency domain.